This invention relates to a method of polymerization of lactide or glycolide (GA, glycolic acid) monomers and in particular to a method of polymerization of one type of the monomers or two types of the monomers using alkyl aluminum catalyst to proceed with bulk or solution polymerization to prepare biodegradable homopolymers or copolymers, and high-molecular-weight homopolymers of polylactide (PLA), polyglycolide (PGA), or copolymers of lactide/glycolide thereof.
Homopolymers or copolymers of lactide or glycolide are non-toxic, biocompatible, and biodegradable. They can be used as biodegradable medical devices such as implant fixation devices, e.g., bone skews, pins, staples, meniscus arrows, bone plates, surgical sutures, etc. There is no way to process conventional polymers of lactide or glycolide to form fixation devices with strong mechanical strength since molecular weights of the polymers are not high and reduced in processing of polymers such as in injection molding and compression molding. It is desirable in the art to seek a novel and simple method of polymerizing lactide or glycolide to prepare high-molecular-weight polylactide or polyglycolide polymer which is non-toxic, biocompatible, biodegradable and has good mechanical strength. The polymer material can be further processed to fixation devices such as bone skews, bone plates, surgical sutures which can be implanted safely and has enough mechanical strength to fix tissues.
The object of the present invention is to provide a method of polymerization of D,L-lactide and/or glycolide using alkyl aluminum catalyst to carry out bulk or solution polymerization to prepare poly(D,L-lactide)-PDLLA, polyglycolide, or copolymers of lactide/glycotide.
The further object of the present invention is to provide a PDLLA homopolymer with a weight-average molecular weight of 900,000-1,000,00. The PDLLA homopolymer is non-toxic, biodegradable and has good biocompatibility and mechanical strength. This polymer material can be used as non-toxic and implantable medical devices and processed by conventional methods such as injection molding or compression molding to prepare fixation devices with good mechanical strength, e.g., bone skews, pins, staples, meniscus arrows, and bone plates, etc.
The PDLLA can be used as guided cell regeneration materials, absorbable sutures, or microtubular tissue regeneration guide channels such as repair of injured nerves, nerve regeneration channels. It can be applied as carriers of drug release control system and reinforcing materials for bone fracture. The other applications of the PDLLA are fibrillar products, burns dressing, absorbant papers or swabs, sponge for hemostasis, and dental packs.
The advantages of the polymerization method of the present invention are simple reaction steps, simple control of the reaction, short reaction time-reaction is complete in 3 to 12 hours. This method can prepare a high-molecular-weight poly(D,L-lactide) homopolymer with good mechanical strength which can be further processed to fixation devices with good mechanical strength. The method can also be applied to polymerize L-lactide monomers to high-molecular-weight poly(L-lactide) homopolymers, D-lactide monomers to high-molecular-weight poly(D-lactide) homopolymers, other lactide monomers to high-molecular-weight polylactide homopolymers, glycolide monomers to high-molecular-weight polyglycolide homopolymers, lactide and glycolide monomers to high-molecular-weight copolymers of lactide/glycolide.